The present invention relates to a device for the osteosynthesis of a spinal segment and more particularly, but not exclusively, a device for osteosynthesis of the spine by the anterior route for the correction of vertebral deformations and degenerations. Among portions of the spine to which these devices may be particularly adapted include the thoracic, thoraco-lumbar, and lumbar spinal segments.
Systems are known in the art which employ rods alone, plates alone, and rod-plates interconnected in such a manner that the plate extends the rod substantially on the longitudinal axis of the latter. Thus the U.S. Pat. No. 5,507,745 describes a rod-plate adapted for an occipito-cervical assembly. The document EP 0,553,042 also teaches the use of a device of the rod-plate type, the plate being in the extension of the longitudinal axis of the rod, this system being particularly adapted for the lumbar-sacral articulation. Once drawback of such rod-plate systems resides in the fact that one of the vertebrae may become undesirably offset relative to the other.
In conventional open surgical interventions involving the removal of a disc, a fusion cage or a graft is placed in position to restore the discal height, and then the two adjacent vertebrae are compressed manually for maintaining in place the bone graft or the cage. Within the framework of the development of surgical interventions by endoscopy and by the anterior route (i.e. with a small-section abdominal opening through which trocars and a closed-circuit micro-television camera are inserted), the compression of the two vertebrae presents a particular difficulty. Heretofore, the surgeons did not add a material or content themselves to stabilize the instrumentation. Thus, there is a need for devices and methods to address these shortcomings.
One form of the present invention is a unique medical treatment device. Other forms include unique osteosynthesis devices and methods.
In another form of the present invention, an osteosynthesis device comprises a rod and a plate disposed substantially parallel to the rod and rigidly connected to the same, and bone anchoring means for engaging the rod and the plate to a spinal segment. Such a system can be equipped with four anchoring elements to address problems regarding relative displacement between vertebrae.
In a further form, a device according to the invention extends over a spinal segment of at least two vertebrae. A surgeon extracts the defective intervertebral disk and then inserts, instead of the disk, a filler, which can be, for example, a bone graft or one or more intersomatic cages. A compression of the graft or the cages is performed to thereby bring the two vertebrae closer together, which vertebrae are thereafter fixed in position.
According to another form, the device comprises means cooperative with the plate for bringing closer together two adjacent vertebrae into each of which an anchorage element is placed; whereby to effect a compression of a filler between the two vertebrae which replaces a removed vertebral disk.
A further form of the invention includes a plate and a rod interconnected at their facing ends by lugs forming with the rod and the plate a substantially rectangular frame, and means for bringing two adjacent vertebrae closer together. Such means may comprise a pair of oblong openings formed in the plate that extend in a direction parallel to the rod in facing relation to each vertebra, and screws adapted to be anchored in the corresponding vertebral body through said openings, the latter and the screws being so arranged that the progressive screwing of the screws brings the two vertebrae closer together. The openings each have a wall defining at its base a ramp which slopes toward the central part of the plate and in the direction toward the surface of the plate bearing against the vertebrae. For this form, the wall/ramp arrangement is formed of a succession of spherical segments and is connected by a cylindrical portion to the bearing surface, and the screws associated with these openings have heads arranged to engage the walls.
Accordingly, one object of the Invention is to provide devices and method for medical treatment procedures.
Another object is to provide a device for osteosynthesis arranged in such a manner as to facilitate compression of adjacent vertebrae.